package com.leetcode.Offer;

public class JZ10_II {
    //优化：可以用两个变量代替前两个数计算
    public int numWays(int n) {
        if (n == 0) {
            return 1;
        } else if (n == 1) {
            return 1;
        } else if (n == 2) {
            return 2;
        }

        int[] dp = new int[n + 1];
        dp[0] = 1;
        dp[1] = 1;
        dp[2] = 2;


        for (int i = 3; i < dp.length; i++) {
            dp[i] = (dp[i - 1] + dp[i - 2]) % 1000000007;
        }

        return dp[n];

    }

    public static void main(String[] args) {
        System.out.println(new JZ10_II().numWays(7));

    }
}
